Phase change ink compositions comprising crystalline sulfone compounds and derivatives thereof

ABSTRACT

A phase change ink composition comprising an amorphous component, a crystalline component comprises a sulfone compound or derivatives thereof, and optionally, a colorant, which are suitable for ink jet printing, including printing on coated paper substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly owned and co-pending, U.S. patentapplication Ser. No. 13/456,619 entitled “Phase Change Ink CompositionsComprising Crystalline Diurethanes And Derivatives Thereof” to NaveenChopra et al., electronically filed on the same day herewith; U.S.patent application Ser. No. 13/457,221 entitled “Phase Change InksComprising Crystalline Amides” to Kentaro Morimitsu et al.,electronically filed on the same day herewith; U.S. patent applicationSer. No. 13/456,916 entitled “Phase Change Ink Compositions ComprisingAromatic Ethers” to Kentaro Morimitsu et al., electronically filed onthe same day herewith; U.S. patent application Ser. No. 13/457,157entitled “Fast Crystallizing Crystalline-Amorphous Ink Compositions andMethods for Making the Same” to Gabriel Iftime et al., electronicallyfiled on the same day herewith; U.S. patent application Ser. No.13/457,271 entitled “Rapid Solidifying Crystalline-Amorphous Inks” toGabriel Iftime et al., electronically filed on the same day herewith;U.S. patent application Ser. No. 8,647,424 entitled “Phase Change InksComprising Inorganic Nucleating Agents” to Daryl W. Vanbesien et al.,electronically filed on the same day herewith; U.S. patent applicationSer. No. 13/456,722 entitled “Phase Change Inks Comprising Fatty Acids”to Gabriel Iftime et al., electronically filed on the same day herewith;U.S. patent application Ser. No. 13/457,300 entitled “Phase Change InksComprising Aromatic Diester Crystalline Compounds” to Kentaro Morimitsuet al., electronically filed on the same day herewith; U.S. patentapplication Ser. No. 13/457,068 entitled “Phase Change Ink CompositionsComprising Diurethanes as Amorphous Materials” to Naveen Chopra et al.,electronically filed on the same day herewith; U.S. patent applicationSer. No. 13/456,805 entitled “Phase Change Inks Comprising OrganicPigments” to Jennifer Belelie et al., electronically filed on the sameday herewith; U.S. patent application Ser. No. 13/456,847 entitled “TROMProcess for Measuring the Rate of Crystallization of Phase Change Inks”to Gabriel Iftime et al., electronically filed on the same day herewith;U.S. patent application Ser. No. 13/456,679 entitled “RapidlyCrystallizing Phase Change Inks and Methods for Forming the Same” toJennifer Belelie et al., electronically filed on the same day herewith;the entire disclosures of which are incorporated herein by reference inits entirety.

BACKGROUND

The present embodiments relate to phase change ink compositionscharacterized by being solid at room temperature (e.g., 20-27° C.) andmolten at an elevated temperature at which the molten ink is applied toa substrate. These phase change ink compositions can be used for ink jetprinting. The present embodiments are directed to a novel phase changeink composition comprising an amorphous component, a crystallinematerial, and optionally a colorant, and methods of making the same. Thecrystalline material comprises sulfone compounds and derivativesthereof.

Ink jet printing processes may employ inks that are solid at roomtemperature and liquid at elevated temperatures. Such inks may bereferred to as solid inks, hot melt inks, phase change inks and thelike. For example, U.S. Pat. No. 4,490,731, the disclosure of which istotally incorporated herein by reference, discloses an apparatus fordispensing phase change ink for printing on a recording medium such aspaper. In piezo ink jet printing processes employing hot melt inks, thephase change ink is melted by the heater in the printing apparatus andutilized (jetted) as a liquid in a manner similar to that ofconventional piezo ink jet printing. Upon contact with the printingrecording medium, the molten ink solidifies rapidly, enabling thecolorant to substantially remain on the surface of the recording mediuminstead of being carried into the recording medium (for example, paper)by capillary action, thereby enabling higher print density than isgenerally obtained with liquid inks. Advantages of a phase change ink inink jet printing are thus elimination of potential spillage of the inkduring handling, a wide range of print density and quality, minimalpaper cockle or distortion, and enablement of indefinite periods ofnonprinting without the danger of nozzle clogging, even without cappingthe nozzles.

In general, phase change inks (sometimes referred to as “hot melt inks”)are in the solid phase at ambient temperature, but exist in the liquidphase at the elevated operating temperature of an ink jet printingdevice. At the jetting temperature, droplets of liquid ink are ejectedfrom the printing device and, when the ink droplets contact the surfaceof the recording medium, either directly or via an intermediate heatedtransfer belt or drum, they quickly solidify to form a predeterminedpattern of solidified ink drops.

Phase change inks for color printing typically comprise a phase changeink carrier composition which is combined with a phase change inkcompatible colorant. In a specific embodiment, a series of colored phasechange inks can be formed by combining ink carrier compositions withcompatible subtractive primary colorants. The subtractive primarycolored phase change inks can comprise four component dyes or pigments,namely, cyan, magenta, yellow and black, although the inks are notlimited to these four colors. These subtractive primary colored inks canbe formed by using a single dye or pigment or a mixture of dyes orpigments. For example, magenta can be obtained by using a mixture ofSolvent Red Dyes or a composite black can be obtained by mixing severaldyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat.No. 5,372,852, the disclosures of each of which are totally incorporatedherein by reference, teach that the subtractive primary colorantsemployed can comprise dyes from the classes of Color Index (C.I.)Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and BasicDyes. The colorants can also include pigments, as disclosed in, forexample, U.S. Pat. No. 5,221,335, the disclosure of which is totallyincorporated herein by reference. U.S. Pat. No. 5,621,022, thedisclosure of which is totally incorporated herein by reference,discloses the use of a specific class of polymeric dyes in phase changeink compositions.

Phase change inks are desirable for ink jet printers because they remainin a solid phase at room temperature during shipping, long term storage,and the like. In addition, the problems associated with nozzle cloggingas a result of ink evaporation with liquid ink jet inks are largelyeliminated, thereby improving the reliability of the ink jet printing.Further, in phase change ink jet printers wherein the ink droplets areapplied directly onto the final recording medium (for example, paper,transparency material, and the like), the droplets solidify immediatelyupon contact with the recording medium, so that migration of ink alongthe printing medium is prevented and dot quality is improved.

While the above conventional phase change ink technology is successfulin producing vivid images and providing economy of jet use and substratelatitude on porous papers, such technology has not been satisfactory forcoated substrates. Thus, while known compositions and processes aresuitable for their intended purposes, a need remains for additionalmeans for forming images or printing on coated paper substrates. Assuch, there is a need to find alternative compositions for phase changeink compositions and future printing technologies to provide customerswith excellent image quality on all substrates, including selecting andidentifying different classes of materials that are suitable for use asdesirable ink components.

There is further a need to provide such phase change ink compositionswhich are suitable for fast printing environments such as productionprinting.

Each of the foregoing U.S. Patents and Patent Publications areincorporated by reference herein. Further, the appropriate componentsand process aspects of the each of the foregoing U.S. Patents and PatentPublications may be selected for the present disclosure in embodimentsthereof.

SUMMARY

According to embodiments illustrated herein, there is provided novelphase change ink compositions comprising crystalline sulfone compoundssuitable for ink jet printing, including printing on coated papersubstrates.

In particular, the present embodiments provide phase change inkcomprising an amorphous component; and a crystalline component being asulfone compound having the following Formula IR₆—SO₂—R₇  Formula Iwherein R₆ and R₇ can be the same or different, and wherein R₆ and R₇each, independently of the other is selected from the group consistingof (i) an alkyl group, which can be a linear or branched, cyclic oracyclic, substituted or unsubstituted, saturated or unsaturated, alkylgroup, and wherein heteroatoms may optionally be present in the alkylgroup having from about 1 to about 40 carbon atoms; (ii) an arylalkylgroup, which can be a substituted or unsubstituted arylalkyl group,wherein the alkyl portion of arylalkyl group can be linear or branched,cyclic or acyclic, substituted or unsubstituted, saturated orunsaturated, and wherein heteroatoms may optionally be present in eitherthe aryl portion or the alkyl portion of the arylalkyl group having fromabout 4 to about 40 carbon atoms; and (iii) an aromatic group, which canbe a substituted or unsubstituted aromatic group, wherein thesubstituent can be a linear, branched, cyclic or acyclic alkyl group andwherein heteroatoms may optionally be present in the aromatic grouphaving from about 3 to about 40 carbon atoms, and mixtures thereof;wherein the phase change ink crystallizes in less than 15 second.

In further embodiments, there is provided a phase change ink comprisingan amorphous component; and a crystalline component being a sulfonecompound having the following Formula IR₆—SO₂—R₇  Formula Ieach R₆ and R₇ is independently alkyl, or aryl, optionally substitutedwith one or more halo, amino, hydroxy, or cyano groups and combinationsthereof, or R₆ and R₇ taken together with the S atom to which they areattached form a heterocyclic ring; wherein the crystalline and amorphouscomponent are present in a crystalline/amorphous weight ratio of fromabout 60:40 to about 95:5.

In yet other embodiments, there is provided a phase change inkcomprising an amorphous component comprises an ester of tartaric acid ofFormula II or an ester of citric acid of Formula III

wherein R₁, R₂, R₃, R₄ and R₅ are independently an alkyl group, whereinthe alkyl can be straight, branched or cyclic, saturated or unsaturated,substituted or unsubstituted, having from about 1 to about 40 carbonatoms, or an substituted or unsubstituted aromatic or heteroaromaticgroup, and mixtures thereof; and

a crystalline component being a sulfone compounds having the followingFormula IR₆—SO₂—R₇  Formula Iwherein R₆ and R₇ can be the same or different, and wherein R₆ and R₇each, independently of the other is selected from the group consistingof (i) an alkyl group, which can be a linear or branched, cyclic oracyclic, substituted or unsubstituted, saturated or unsaturated, alkylgroup, and wherein heteroatoms may optionally be present in the alkylgroup having from about 1 to about 40 carbon atoms; (ii) an arylalkylgroup, which can be a substituted or unsubstituted arylalkyl group,wherein the alkyl portion of arylalkyl group can be linear or branched,cyclic or acyclic, substituted or unsubstituted, saturated orunsaturated, and wherein heteroatoms may optionally be present in eitherthe aryl portion or the alkyl portion of the arylalkyl group having fromabout 4 to about 40 carbon atoms; and (iii) an aromatic group, which canbe a substituted or unsubstituted aromatic group, wherein thesubstituent can be a linear, branched, cyclic or acyclic alkyl group andwherein heteroatoms may optionally be present in the aromatic grouphaving from about 3 to about 40 carbon atoms and mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present embodiments, certainembodiments thereof are shown in the accompanying drawings.

FIG. 1 is differential scanning calorimetry (DSC) data of diphenylsulfone confirming phase changing properties according to the presentembodiments (the DSC data was obtained on a Q1000 Differential Scanningcalorimeter (TA Instruments) at a rate of 10° C./min from −50 to 200 to−50° C.);

FIG. 2 illustrates the TROM process showing images of crystallineformation from crystallization onset to crystallization completionaccording to an embodiment of the disclosure.

FIG. 3 is DSC data of a phase change ink sample made according to thepresent embodiments (the DSC data was obtained on a Q1000 DifferentialScanning calorimeter (TA Instruments) at a rate of 10° C./min from −50to 200 to −50° C.); and

FIG. 4 is a graph illustrating rheology data of phase change ink samplesmade according to the present embodiments.

All of the rheology measurements were made on a RFS3 Rheometer (TAinstruments), using a 25 mm parallel plate, at a frequency of 1 Hz; themethod used was a temperature sweep from high to low temperatures, intemperature steps of 5° C., a soak (equilibration) time of 120 secondsbetween each temperature and at a constant frequency of 1 Hz).

DETAILED DESCRIPTION

In the following description, it is understood that other embodimentsmay be utilized and structural and operational changes may be madewithout departure from the scope of the present embodiments disclosedherein.

As used herein, the term “alkyl” refers to an aliphatic hydrocarbongroup. The alkyl moiety may be a “saturated alkyl” group, which meansthat it does not contain any alkene or alkyne moieties. The alkyl moietymay also be an “unsaturated alkyl” moiety, which means that it containsat least one alkene or alkyne moiety. An “alkene” moiety refers to agroup consisting of at least two carbon atoms and at least onecarbon-carbon double bond, and an “alkyne” moiety refers to a groupconsisting of at least two carbon atoms and at least one carbon-carbontriple bond. The alkyl moiety, whether saturated or unsaturated, may bebranched, straight chain, or cyclic.

The alkyl group may have 1 to 40 carbon atoms (whenever it appearsherein, a numerical range such as “1 to 40” refers to each integer inthe given range; e.g., “1 to 40 carbon atoms” means that the alkyl groupmay consist of 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., upto and including 40 carbon atoms, although the present definition alsocovers the occurrence of the term “alkyl” where no numerical range isdesignated). The alkyl group may also be a medium size alkyl having 1 to10 carbon atoms. The alkyl group could also be a lower alkyl having 1 to4 carbon atoms. The alkyl group of the compounds of the invention may bedesignated as “C₁-C₄ alkyl” or similar designations. By way of exampleonly, “C₁-C₄ alkyl” indicates that there are one to four carbon atoms inthe alkyl chain, i.e., the alkyl chain is selected from the groupconsisting of methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl,sec-butyl, and t-butyl.

The alkyl group may be substituted or unsubstituted. When substituted,any group(s) besides hydrogen can be the substitutent group(s). Whensubstituted, the substituent group(s) is (are) one or more group(s)individually and independently selected from the following non-limitingillustrative list: alkyl, cycloalkyl, hydroxy, alkoxy, cyano, halo, andamino, including mono- and di-substituted amino groups. Typical alkylgroups include, but are in no way limited to, methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tertiary butyl, pentyl, hexyl, ethenyl,propenyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, andthe like. Each substituent group may be further substituted.

The term “aryl,” as used herein, alone or in combination, means acarbocyclic aromatic system containing one, two or three rings whereinsuch rings may be attached together in a pendent manner or may be fused.The term “aryl,” embraces aromatic radicals such as benzyl, phenyl,naphthyl, anthracenyl, and biphenyl.

The term “arylalkyl” as used herein, alone or in combination, refers toan aryl group attached to the parent molecular moiety through an alkylgroup.

The term “halo” or, alternatively, “halogen” means fluoro, chloro, bromoor iodo.

Phase change ink technology broadens printing capability and customerbase across many markets, and the diversity of printing applicationswill be facilitated by effective integration of printhead technology,print process and ink materials. The phase change ink compositions arecharacterized by being solid at room temperature and molten at anelevated temperature at which the molten ink is applied to a substrate.As discussed above, while current ink options are successful for porouspaper substrates, these options are not always satisfactory for coatedpaper substrates.

It was previously discovered that using a mixture of crystalline andamorphous small molecule compounds in solid ink formulations providesrobust inks, and in particular, solid inks which demonstrate robustimages on coated paper. (U.S. patent application Ser. No. 13/095,636entitled “Solid Ink Compositions Comprising Crystalline-AmorphousMixtures” to Jennifer L. Belelie et. al., filed Apr. 27, 2011. Printsamples made with such phase change inks demonstrate better robustnesswith respect to scratch, fold, and fold offset as compared to currentlyavailable phase change inks.

However, the present inventors discovered that in many cases mixturesmade of crystalline and amorphous materials with optional dye colorantsolidify slowly when printed on substrates from a molten state. Suchslow solidifying inks are not suitable for high speed printingenvironments, like for example production printing, where printing atspeeds higher than 100 feet per minute is required. Solidification ofthe ink is due to crystallization of the crystalline component in theink when cooling.

The inventors have found that fast crystallization of a composition madeof a crystalline and an amorphous component is not an inherent propertyof the composition.

The present embodiments provide novel phase change ink compositionscomprising crystalline sulfone materials and amorphous materials whichcrystallize fast and are therefore suitable for high speed ink jetprinting, including printing on coated paper.

The present embodiments provide a new type of ink jet phase change inkcomposition which comprises a blend of (1) crystalline and (2) amorphouscomponents, generally in a weight ratio of from about 60:40 to about95:5, respectively. In more specific embodiments, the weight ratio ofthe crystalline to amorphous component is from about 65:35 to about95:5, or is from about 70:30 to about 90:10. In other embodiments, thecrystalline and amorphous components are blended in a weight ratio offrom about 1.5 to about 20 or from about 2.0 to about 10, respectively.Each component imparts specific properties to the phase change inks, andthe blend of the components provides inks that exhibit excellentrobustness on uncoated and coated substrates. The crystalline componentin the ink formulation drives the phase change through rapidcrystallization on cooling. The crystalline component also sets up thestructure of the final ink film and creates a hard ink by reducing thetackiness of the amorphous component. The amorphous components providetackiness and impart robustness to the printed ink.

The present embodiments comprise crystalline materials selected from thegroup of sulfone compounds. These crystalline materials have been foundto demonstrate good phase transition as well as have specific thermaland rheological properties that make the materials suitable for use inphase change inks. For example, the crystalline materials show sharpcrystallization, relatively low viscosity (≦10¹ centipoise (cps), orfrom about 0.5 to about 20 cps, or from about 1 to about 15 cps) at atemperature of about 140° C., but very high viscosity (>10⁶ cps) at roomtemperature. These materials have a melting temperature (T_(melt)) ofless than 150° C., or from about 65 to about 150° C., or from about 66to about 145° C., and a crystallization temperature (T_(crys)) ofgreater than 60° C., or from about 60 to about 140° C., or from about 65to about 120° C. The ΔT between T_(melt) and T_(crys) is less than about55° C.

In embodiments, the sulfone compound has a general Formula IR₆—SO₂—R₇  Formula Iwherein R₆ and R₇ can be the same or different, and wherein R₆ and R₇each, independently of the other is selected from the group consistingof (i) an alkyl group, which can be a linear or branched, cyclic oracyclic, substituted or unsubstituted, saturated or unsaturated, alkylgroup, and wherein heteroatoms may optionally be present in the alkylgroup, in embodiments, having from about 1 to about 40 carbon atoms,from about 1 to about 20 carbon atoms, or from about 1 to about 10carbon atoms, although the numbers can be outside of these ranges, (ii)an arylalkyl group, which can be a substituted or unsubstitutedarylalkyl group, wherein the alkyl portion of arylalkyl group can belinear or branched, cyclic or acyclic, substituted or unsubstituted,saturated or unsaturated, and wherein heteroatoms may optionally bepresent in either the aryl portion or the alkyl portion of the arylalkylgroup, in embodiments, having from about 4 to about 40 carbon atoms,from about 7 to about 20 carbon atoms, or from about 7 to about 12carbon atoms, although the numbers can be outside of these ranges; and(iii) an aromatic group, which can be a substituted or unsubstitutedaromatic group, wherein the substituent can be a linear, branched,cyclic or acyclic alkyl group and wherein heteroatoms may optionally bepresent in the aromatic group, having from about 3 to from about 40carbon atoms, from about 6 to about 20 carbon atoms, or about 6 to about10 carbon atoms, although the numbers can be outside of these ranges,and mixtures thereof.

In certain embodiments, each R₆ and R₇ is independently alkyl, or aryl,optionally substituted with one or more halo, amino, hydroxy, or cyanogroups and combinations thereof, or R₆ and R₇ taken together with the Satom to which they are attached form a heterocyclic ring (e.g.,sulfolane, 3-sulfolene, etc.). In certain of such embodiments, each R₆and R₇ is independently an optionally substituted alkyl, such as,methyl, ethyl, isopropyl, n-butyl, t-butyl or vinyl, optionallysubstituted with one or more hydroxyl, cyano, or combinations thereof.In certain of such embodiments, each R₆ and R₇ is independently anoptionally substituted aryl, such as, phenyl, or benzyl. In certainembodiments, each R₆ and R₇ is independently substituted with one ormore amino, chloro, fluoro, hydroxy, cyano or combinations thereof.Substitution on the aryl groups may be made in the ortho, meta or paraposition of the phenyl groups and combinations thereof. In certainembodiments, each R₆ and R₇ is independently 2-hydroxyethyl, orcyanomethyl.

In certain embodiments, the crystalline component may include diphenylsulfone, dimethyl sulfone, bis(4-hydroxyphenyl)sulfone,bis(4-aminophenyl)sulfone, bis(3-aminophenyl)sulfone,bis(4-chlorophenyl)sulfone, bis(4-fluorophenyl)sulfone,2-hydroxyphenyl-4-hydroxyphenyl sulfone, phenyl-4-chlorophenyl sulfone,phenyl-2-aminophenyl sulfone, bis(3-amino-4-hydroxyphenyl)sulfone,dibenzyl sulfone, methylethyl sulfone, diethyl sulfone, methylisopropylsulfone, ethylisopropyl sulfone, di-n-butyl sulfone, divinyl sulfone,methyl-2-hydroxyethyl sulfone, methylchloromethyl sulfone, sulfolane,3-sulfolene, and mixtures thereof.

In combination with the crystalline materials of the presentembodiments, amorphous materials are also used. Any amorphous componentsuitable for use in phase change ink may be used.

The Amorphous Compound

The amorphous compound may comprise an ester of tartaric acid of FormulaII or an ester of citric acid of Formula III

wherein each R₁, R₂, R₃, R₄, and R₅ is independently an alkyl group,wherein the alkyl can be straight, branched or cyclic, saturated orunsaturated, substituted or unsubstituted, having from about 1 to about40 carbon atoms, or an substituted or unsubstituted aromatic orheteroaromatic group, and mixtures thereof. In certain embodiments, eachR₁, R₂ R₃, R₄ and R₅ is independently a cyclohexyl group optionallysubstituted with one or more alkyl groups selected from methyl, ethyl,n-propyl, isopropyl, n-butyl and t-butyl. In certain embodiments, eachR₁, R₂, R₃, R₄ and R₅ is independently a cyclohexyl group optionallysubstituted with one or more alkyl groups selected from methyl, ethyl,n-propyl, isopropyl, n-butyl and t-butyl. In certain embodiments, R₁, R₂R₃, R₄ and R are each 2-isopropyl-5-methylcyclohexyl or a mixture of4-t-butylcyclohexyl and cyclohexyl.

Referring to Formula II, in certain embodiments, one of R₁ and R₂ is2-isopropyl-5-methylcyclohexyl, and the other one of R₁ and R₂ is2-isopropyl-5-methylcyclohexyl, 4-t-butylcyclohexyl, or cyclohexyl, orone of R₁ and R₂ is 4-t-butylcyclohexyl, and the other one of R1 and R2is cyclohexyl. In certain embodiment, R₁ and R₂ are each2-isopropyl-5-methylcyclohexyl. In certain embodiment, R₁ is2-isopropyl-5-methylcyclohexyl and R₂ is 4-t-butylcyclohexyl. In certainembodiment, R₁ is 2-isopropyl-5-methylcyclohexyl and R₂ is cyclohexyl.In certain embodiment, R₁ is 4-t-butylcyclohexyl and R₂ is cyclohexyl.

Referring to Formula III, in certain embodiments, one of R₃, R₄ and R₅is 2-isopropyl-5-methylcyclohexyl, and the other one of R₃, R₄ and R₅ is2-isopropyl-5-methylcyclohexyl, 4-t-butylcyclohexyl, or cyclohexyl, orone of R₃, R₄ and R₅ is 4-t-butylcyclohexyl, and the other one of R₃, R₄and R₅ is cyclohexyl. In certain embodiment, R₃, R₄ and R₅ are each2-isopropyl-5-methylcyclohexyl. In certain embodiment, R₃ is2-isopropyl-5-methylcyclohexyl and R₄ and R₅ are each4-t-butylcyclohexyl. In certain embodiment, R₃ is2-isopropyl-5-methylcyclohexyl and R₄ and R₅ are each cyclohexyl. Incertain embodiment, R3 is 4-t-butylcyclohexyl and R₄ and R₅ are eachcyclohexyl.

Some suitable amorphous materials are disclosed in U.S. patentapplication Ser. No. 13/095,784 to Morimitsu et al., which is herebyincorporated by reference in its entirety. The amorphous materials maycomprise an ester of tartaric acid having a formula of

wherein R₁ and R₂ each, independently of the other or meaning that theycan be the same or different, is selected from the group consisting ofalkyl group, wherein the alkyl portion can be straight, branched orcyclic, saturated or unsaturated, substituted or unsubstituted, havingfrom about 1 to about 40 carbon atoms, or an substituted orunsubstituted aromatic or heteroaromatic group, and mixtures thereof. Incertain embodiments, each R₁ and R₂ is independently a cyclohexyl groupoptionally substituted with one or more alkyl group(s) selected frommethyl, ethyl, n-propyl, isopropyl, n-butyl and t-butyl. In certainembodiments, R₁ and R₂ are each 2-isopropyl-5-methylcyclohexyl.

The tartaric acid backbone is selected from L-(+)-tartaric acid,D-(−)-tartaric acid, DL-tartaric acid, or mesotartaric acid, andmixtures thereof. Depending on the R groups and the stereochemistries oftartaric acid, the esters could form crystals or stable amorphouscompounds. In specific embodiments, the amorphous compound is selectedfrom the group consisting of di-L-menthyl L-tartrate, di-DL-menthylL-tartrate (DMT), di-L-menthyl DL-tartrate, di-DL-menthyl DL-tartrate,and any stereoisomers and mixtures thereof.

The amorphous compound may comprise an ester of citric acid disclosed inU.S. patent application Ser. No. 13/095,795 to Morimitsu et al., whichis hereby incorporated by reference in its entirety. These amorphousmaterials are synthesized by an esterification reaction of citric acid.In particular, citric acid was reacted with a variety of alcohols tomake tri-esters according to the synthesis scheme shown in U.S. patentapplication Ser. No. 13/095,795. The amorphous compounds are synthesizedby an esterification reaction of tartaric acid. These materials showrelatively low viscosity (<10² centipoise (cps), or from about 1 toabout 100 cps, or from about 5 to about 95 cps) near the jettingtemperature (≦140° C., or from about 100 to about 140° C., or from about105 to about 140° C.) but very high viscosity (>10⁵ cps) at roomtemperature.

In particular, di-DL-menthyl L-tartrate (DMT) was found to be especiallysuitable for use as an amorphous compound in the present inkembodiments.

To synthesize the amorphous component, tartaric acid was reacted with avariety of alcohols to make di-esters as shown in the synthesis schemeshown in U.S. patent application Ser. No. 13/095,784. A variety ofalcohols may be used in the esterification such as, for example,menthol, isomenthol, neomenthol, isoneomenthol, and any stereoisomersand mixtures thereof. Mixtures of aliphatic alcohols may be used in theesterification. For example, a mixture of two aliphatic alcohols may beused in the esterification. The molar ratios of the aliphatic alcoholsmay be from 25:75 to 75:25, from 40:60 to 60:40, or about 50:50.Examples of suitable aliphatic alcohol whose mixtures form amorphouscompounds when reacted with tartaric acid include cyclohexanol andsubstituted cyclohexanol (e.g., 2-, 3-, or 4-tert-butyl-cyclohexanol).In embodiments, two or more molar equivalents of alcohol may be used inthe reaction to produce the di-esters of tartaric acid. If one molarequivalent of alcohol is used, the result is mostly mono-esters.

Other suitable amorphous components include those disclosed in U.S.patent application Ser. No. 13/095,795 to Morimitsu et al., which ishereby incorporated by reference in its entirety. The amorphousmaterials may comprise a compound having the following structure:

R₃, R₄ and R₅ are independently an alkyl group, wherein the alkyl can bestraight, branched or cyclic, saturated or unsaturated, substituted orunsubstituted, having from about 1 to about 40 carbon atoms, or ansubstituted or unsubstituted aromatic or heteroaromatic group, andmixtures thereof.

These amorphous materials are synthesized by an esterification reactionof citric acid. In particular, citric acid was reacted with a variety ofalcohols to make tri-esters according to the synthesis scheme disclosedtherein. In embodiments, the phase change ink composition is obtained byusing amorphous compounds synthesized from citric acid and at least onealcohol in an esterification reaction.

The crystalline and amorphous materials of the present embodiments werefound to be miscible with one another in the liquid state. The resultingink compositions formulated with the crystalline and amorphous materialsshow good rheological profiles. Image samples created by the phasechange ink composition on coated paper by K-proof exhibit excellentrobustness. A K-proofer is a common test fixture in a print shop. Inthis case the K-proofer has been modified to heat the printing plate tomelt the phase change ink. The K-Proofer used has three rectangulargravure patterns each approximately 9.4×4.7 cm. The cell density of thefirst rectangle is nominally 100%, the second 80%, and the third 60%. Inpractice this K-proof plate results in films (or pixels) of about 5microns in thickness (or height). Test ink is spread over the heatedgravure plate and a test print is made by passing a wiping blade acrossthe plate surface immediately followed by a rubber roll upon which atest paper has been secured. As the paper roll passes ink is transferredfrom the gravure cells to the paper.

The present embodiments comprise a balance of amorphous and crystallinematerials to realize a sharp phase transition from liquid to solid andfacilitate hard and robust printed images, while maintaining a desiredlevel of viscosity. Prints made with this ink demonstrated advantagesover commercially available inks, such as for example, better robustnessagainst scratch. Thus, the present aromatic ethers, which providecrystalline components for the phase change inks, have been discoveredto produce robust inks having desirable rheological profiles and thatmeet the many requirements for inkjet printing.

In embodiments, the crystalline material is present an amount of fromabout 60 percent to about 95 percent by weight, or from about 65 percentto about 95 percent by weight, or from about 70 percent to about 90percent by weight of the total weight of the ink composition. Inembodiments, the amorphous material is present in an amount of fromabout 5 percent to about 40 percent by weight, or from about 5 percentto about 35 percent by weight, or from about 10 percent to about 30percent by weight of the total weight of the ink composition

In embodiments, in the molten state, the resulting solid ink has aviscosity of from about 1 to about 22 cps, or from about 4 to about 15cps, or from about 6 to about 12 cps, at a the jetting temperature. Thejetting temperature is typically comprised in a range from about 100° C.to about 140° C. In embodiments, the solid ink has a viscosity of about>10⁶ cps, at room temperature. In embodiments, the solid ink has aT_(melt) of from about 65 to about 140° C., or from about 70 to about140° C., from about 80 to about 135° C. and a T_(crys) of from about 40to about 140° C., or from about 45 to about 130° C., from about 50 toabout 120° C., as determined by DSC at a rate of 10° C./min.

While sulfone compounds are known in the literature and from commercialsources, the properties of this class compounds vary depending onchemical structures. The present inventors have discovered specificcrystalline sulfone compounds and derivatives thereof that meet therequirements for use as the crystalline material in phase change inkcompositions. The primary requirement for phase change ink is that it isin the liquid state at jetting temperature (typically from about 100 toabout 140° C.) and solid state at room temperature. The suitablecandidates identified for use in the present embodiments are listed inTable 1. All compounds identified are commercially available from TCIAmerica (Portland, Oreg.) or Sigma-Aldrich.

TABLE 1 Compound T_(melt) T_(crys) T_(melt) − T_(crys) Miscibility with# Structure (° C.)* (° C.)* (° C.) amorphous** 1

127 77 50 Miscible 2

113 79 34 Not miscible *Determined by DSC at a rate of 10° C./min.**Miscibility with tri-DL-menthyl citrate (TMC) and di-DL-menthylL-tartrate (DMT) in molten states.

Other sulfone derivatives are also commercially available with T_(melt)data. Table 2 provides a list of sulfone derivatives having the generalformula R₆—SO₂—R₇. As shown in Table 2, T_(melt) varies by introducingdifferent substituents, changing alkyl chain length, having asymmetricalstructures, or forming cyclic structures.

TABLE 2 Melting temperatures of sulfones (R₆—SO₂—R₇) Compound # R₆ R₇T_(melt) (° C.)* 3 4-Hydroxyphenyl 4-Hydroxyphenyl 247 4 4-Aminophenyl4-Aminophenyl 177 5 3-Aminophenyl 3-Aminophenyl 172 6 4-Chlorophenyl4-Chlorophenyl 148 7 4-Fluorophenyl 4-Fluorophenyl 99 8 2-Hydroxyphenyl4-Hydroxyphenyl 184 9 4-Chlorophenyl Phenyl 92 10 2-Aminophenyl Phenyl119 11 3-Amino-4- 3-Amino-4- 231 hydroxyphenyl hydroxyphenyl 12 BenzylBenzyl ** 13 Ethyl Methyl 34 14 Ethyl Ethyl 73 15 Isopropyl Methyl ***16 Isopropyl Ethyl *** 17 n-Butyl n-Butyl 43 18 Vinyl Vinyl −26(e.g.—CH═CH₂) (e.g.—CH═CH₂) 19 2-Hydroxyethyl Methyl 21 20 CyanomethylMethyl 84 21 —CH₂—CH₂—CH₂—CH₂— 20-26 22 —CH₂—CH═CH—CH₂— 65 * Meltingpoint data from commercial source. ** Data not available. Solid at roomtemperature. *** Data not available. Liquid at room temperature.

Compounds 7, 9, 10, 14 and 20 demonstrated the most promising meltingtemperatures. The above list, while illustrative, does not include allof the possible chemical structures of sulfone compounds that would begood candidates as the crystalline component of phase change ink.

DSC was employed to measure thermal properties of the materials. Asshown in FIG. 1, Compound 1 (diphenyl sulfone) exhibited very sharptransitions within the desirable temperature range indicating goodproperties for the phase changing material of the ink. The relativelynarrow gap between T_(melt) and T_(cryst) translates to a rapid phasechange, making this material an especially suitable candidate for thecrystalline component of the ink. Compound 2 also showed very promisingthermal properties, however the compound did not blend as well with theamorphous materials (e.g., tri-DL-menthyl citrate and di-DL-menthylL-tartrate) used as did Compound 1.

The ink of embodiments may further include conventional additives totake advantage of the known functionality associated with suchconventional additives. Such additives may include, for example, atleast one antioxidant, defoamer, slip and leveling agents, clarifier,viscosity modifier, adhesive, plasticizer and the like.

The ink may optionally contain antioxidants to protect the images fromoxidation and also may protect the ink components from oxidation whileexisting as a heated melt in the ink reservoir. Examples of suitableantioxidants include N,N′-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide) (IRGANOX 1098, available from BASF),2,2-bis(4-(2-(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyloxy))ethoxyphenyl)propane(TOPANOL-205, available from Vertellus),tris(4-tert-butyl-3-hydroxy-2,6-dimethyl benzyl)isocyanurate (Aldrich),2,2′-ethylidene bis(4,6-di-tert-butylphenyl)fluoro phosphonite(ETHANOX-398, available from Albermarle Corporation),tetrakis(2,4-di-tert-butylphenyl)-4,4′-biphenyl diphosphonite (ALDRICH46), pentaerythritol tetrastearate (TCI America), tributylammoniumhypophosphite (Aldrich), 2,6-di-tert-butyl-4-methoxyphenol (Aldrich),2,4-di-tert-butyl-6-(4-methoxybenzyl)phenol (Aldrich),4-bromo-2,6-dimethylphenol (Aldrich), 4-bromo-3,5-didimethylphenol(Aldrich), 4-bromo-2-nitrophenol (Aldrich), 4-(diethylaminomethyl)-2,5-dimethylphenol (Aldrich), 3-dimethylaminophenol(Aldrich), 2-amino-4-tert-amylphenol (Aldrich),2,6-bis(hydroxymethyl)-p-cresol (Aldrich), 2,2′-methylenediphenol(Aldrich), 5-(diethylamino)-2-nitrosophenol (Aldrich),2,6-dichloro-4-fluorophenol (Aldrich), 2,6-dibromo fluoro phenol(Aldrich), α-trifluoro-o-creso-1 (Aldrich), 2-bromo-4-fluorophenol(Aldrich), 4-fluorophenol (Aldrich),4-chlorophenyl-2-chloro-1,1,2-tri-fluoroethyl sulfone (Aldrich),3,4-difluoro phenylacetic acid (Adrich), 3-fluorophenylacetic acid(Aldrich), 3,5-difluoro phenylacetic acid (Aldrich),2-fluorophenylacetic acid (Aldrich), 2,5-bis(trifluoromethyl) benzoicacid (Aldrich),ethyl-2-(4-(4-(trifluoromethyl)phenoxy)phenoxy)propionate (Aldrich),tetrakis (2,4-di-tert-butyl phenyl)-4,4′-biphenyl diphosphonite(Aldrich), 4-tert-amyl phenol (Aldrich),3-(2H-benzotriazol-2-yl)-4-hydroxy phenethylalcohol (Aldrich), NAUGARD76, NAUGARD 445, NAUGARD 512, AND NAUGARD 524 (manufactured by ChemturaCorporation), and the like, as well as mixtures thereof. Theantioxidant, when present, may be present in the ink in any desired oreffective amount, such as from about 0.25 percent to about 10 percent byweight of the ink or from about 1 percent to about 5 percent by weightof the ink.

In embodiments, the phase change ink compositions described herein mayalso include a colorant. Any desired or effective colorant can beemployed in the phase change ink compositions, including dyes, pigments,mixtures thereof, and the like, provided that the colorant can bedissolved or dispersed in the ink carrier. Any dye or pigment may bechosen, provided that it is capable of being dispersed or dissolved inthe ink carrier and is compatible with the other ink components. Thephase change carrier compositions can be used in combination withconventional phase change ink colorant materials, such as Color Index(C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, BasicDyes, Sulphur Dyes, Vat Dyes, and the like. Examples of suitable dyesinclude Neozapon Red 492 (BASF); Orasol Red G (Pylam Products); DirectBrilliant Pink B (Oriental Giant Dyes); Direct Red 3BL (ClassicDyestuffs); Supranol Brilliant Red 3BW (Bayer AG); Lemon Yellow 6G(United Chemie); Light Fast Yellow 3G (Shaanxi); Aizen Spilon YellowC-GNH (Hodogaya Chemical); Bemachrome Yellow GD Sub (Classic Dyestuffs);Cartasol Brilliant Yellow 4GF (Clariant); Cibanone Yellow 2G (ClassicDyestuffs); Orasol Black RLI (BASF); Orasol Black CN (Pylam Products);Savinyl Black RLSN (Clariant); Pyrazol Black BG (Clariant); MorfastBlack 101 (Rohm & Haas); Diaazol Black RN (ICI); Thermoplast Blue 670(BASF); Orasol Blue GN (Pylam Products); Savinyl Blue GLS (Clariant);Luxol Fast Blue MBSN (Pylam Products); Sevron Blue 5GMF (ClassicDyestuffs); Basacid Blue 750 (BASF); Keyplast Blue (Keystone AnilineCorporation); Neozapon Black X51 (BASF); Classic Solvent Black 7(Classic Dyestuffs); Sudan Blue 670 (C.I. 61554) (BASF); Sudan Yellow146 (C.I. 12700) (BASF); Sudan Red 462 (C.I. 26050) (BASF); C.I.Disperse Yellow 238; Neptune Red Base NB543 (BASF, C.I. Solvent Red 49);Neopen Blue FF-4012 (BASF); Lampronol Black BR (C.I. Solvent Black 35)(ICI); Morton Morplas Magenta 36 (C.I. Solvent Red 172); metalphthalocyanine colorants such as those disclosed in U.S. Pat. No.6,221,137, the disclosure of which is totally incorporated herein byreference, and the like. Polymeric dyes can also be used, such as thosedisclosed in, for example, U.S. Pat. No. 5,621,022 and U.S. Pat. No.5,231,135, the disclosures of each of which are herein entirelyincorporated herein by reference, and commercially available from, forexample, Milliken & Company as Milliken Ink Yellow 869, Milliken InkBlue 92, Milliken Ink Red 357, Milliken Ink Yellow 1800, Milliken InkBlack 8915-67, uncut Reactint Orange X-38, uncut Reactint Blue X-17,Solvent Yellow 162, Acid Red 52, Solvent Blue 44, and uncut ReactintViolet X-80.

Pigments are also suitable colorants for the phase change inks. Examplesof suitable pigments include PALIOGEN Violet 5100 (BASF); PALIOGENViolet 5890 (BASF); HELIOGEN Green L8730 (BASF); LITHOL Scarlet D3700(BASF); SUNFAST Blue 15:4 (Sun Chemical); Hostaperm Blue B2G-D(Clariant); Hostaperm Blue B4G (Clariant); Permanent Red P-F7RK;Hostaperm Violet BL (Clariant); LITHOL Scarlet 4440 (BASF); Bon Red C(Dominion Color Company); ORACET Pink RF (BASF); PALIOGEN Red 3871 K(BASF); SUNFAST Blue 15:3 (Sun Chemical); PALIOGEN Red 3340 (BASF);SUNFAST Carbazole Violet 23 (Sun Chemical); LITHOL Fast Scarlet L4300(BASF); SUNBRITE Yellow 17 (Sun Chemical); HELIOGEN Blue L6900, L7020(BASF); SUNBRITE Yellow 74 (Sun Chemical); SPECTRA PAC C Orange 16 (SunChemical); HELIOGEN Blue K6902, K6910 (BASF); SUNFAST Magenta 122 (SunChemical); HELIOGEN Blue D6840, D7080 (BASF); Sudan Blue OS (BASF);NEOPEN Blue FF4012 (BASF); PV Fast Blue B2GO1 (Clariant); IRGALITE BlueGLO (BASF); PALIOGEN Blue 6470 (BASF); Sudan Orange G (Aldrich), SudanOrange 220 (BASF); PALIOGEN Orange 3040 (BASF); PALIOGEN Yellow 152,1560 (BASF); LITHOL Fast Yellow 0991 K (BASF); PALIOTOL Yellow 1840(BASF); NOVOPERM Yellow FGL (Clariant); Ink Jet Yellow 4G VP2532(Clariant); Toner Yellow HG (Clariant); Lumogen Yellow D0790 (BASF);Suco-Yellow L1250 (BASF); Suco-Yellow D1355 (BASF); Suco Fast YellowD1355, D1351 (BASF); HOSTAPERM Pink E 02 (Clariant); Hansa BrilliantYellow 5GX03 (Clariant); Permanent Yellow GRL 02 (Clariant); PermanentRubine L6B 05 (Clariant); FANAL Pink D4830 (BASF); CINQUASIA Magenta (DUPONT); PALIOGEN Black L0084 (BASF); Pigment Black K801 (BASF); andcarbon blacks such as REGAL 330™ (Cabot), Nipex 150 (Evonik) CarbonBlack 5250 and Carbon Black 5750 (Columbia Chemical), and the like, aswell as mixtures thereof.

Pigment dispersions in the ink base may be stabilized by synergists anddispersants. Generally, suitable pigments may be organic materials orinorganic. Magnetic material-based pigments are also suitable, forexample, for the fabrication of robust Magnetic Ink CharacterRecognition (MICR) inks. Magnetic pigments include magneticnanoparticles, such as for example, ferromagnetic nanoparticles.

Also suitable are the colorants disclosed in U.S. Pat. No. 6,472,523,U.S. Pat. No. 6,726,755, U.S. Pat. No. 6,476,219, U.S. Pat. No.6,576,747, U.S. Pat. No. 6,713,614, U.S. Pat. No. 6,663,703, U.S. Pat.No. 6,755,902, U.S. Pat. No. 6,590,082, U.S. Pat. No. 6,696,552, U.S.Pat. No. 6,576,748, U.S. Pat. No. 6,646,111, U.S. Pat. No. 6,673,139,U.S. Pat. No. 6,958,406, U.S. Pat. No. 6,821,327, U.S. Pat. No.7,053,227, U.S. Pat. No. 7,381,831 and U.S. Pat. No. 7,427,323, thedisclosures of each of which are incorporated herein by reference intheir entirety.

In embodiments, solvent dyes are employed. An example of a solvent dyesuitable for use herein may include spirit soluble dyes because of theircompatibility with the ink carriers disclosed herein. Examples ofsuitable spirit solvent dyes include Neozapon Red 492 (BASF); Orasol RedG (Pylam Products); Direct Brilliant Pink B (Global Colors); AizenSpilon Red C-BH (Hodogaya Chemical); Kayanol Red 3BL (Nippon Kayaku);Spirit Fast Yellow 3G; Aizen Spilon Yellow C-GNH (Hodogaya Chemical);Cartasol Brilliant Yellow 4GF (Clariant); Pergasol Yellow 5RA EX(Classic Dyestuffs); Orasol Black RLI (BASF); Savinyl Black RLS(Clariant); Morfast Black 101 (Rohm and Haas); Orasol Blue GN (PylamProducts); Thermoplast Blue 670 (BASF); Savinyl Blue GLS (Sandoz); LuxolFast Blue MBSN (Pylam); Sevron Blue 5GMF (Classic Dyestuffs); BasacidBlue 750 (BASF); Keyplast Blue E (Keystone Aniline Corporation);Neozapon Black X51 (C.I. Solvent Black, C.I. 12195) (BASF); Sudan Blue670 (C.I. 61554) (BASF); Sudan Yellow 146 (C.I. 12700) (BASF); Sudan Red462 (C.I. 260501) (BASF), mixtures thereof and the like.

The colorant may be present in the phase change ink in any desired oreffective amount to obtain the desired color or hue such as, forexample, at least from about 0.1 percent by weight of the ink to about50 percent by weight of the ink, at least from about 0.2 percent byweight of the ink to about 20 percent by weight of the ink, and at leastfrom about 0.5 percent by weight of the ink to about 10 percent byweight of the ink.

In embodiments, in the molten state, the ink carriers for the phasechange inks may have a viscosity of from about 1 to, about 22 cps, orfrom about 4 to about 15 cps, or from about 6 to about 12 cps, at a thejetting temperature. The jetting temperature is typically comprised in arange from about 100° C. to about 140° C. In embodiments, the solid inkhas a viscosity of about >106 cps, at room temperature. In embodiments,the solid ink has a Tmelt of from about 65 to about 140° C., or fromabout 70 to about 140° C., from about 80 to about 135° C. and a Tcrys offrom about 40 to about 140° C., or from about 45 to about 130° C., fromabout 50 to about 120° C., as determined by DSC at a rate of 10° C./min.

The ink compositions can be prepared by any desired or suitable method.For example, each of the components of the ink carrier can be mixedtogether, followed by heating, the mixture to at least its meltingpoint, for example from about 60° C. to about 150° C., 80° C. to about145° C. and 85° C. to about 140° C. The colorant may be added before theink ingredients have been heated or after the ink ingredients have beenheated. When pigments are the selected colorants, the molten mixture maybe subjected to grinding in an attritor or ball mill apparatus or otherhigh energy mixing equipment to affect dispersion of the pigment in theink carrier. The heated mixture is then stirred for about 5 seconds toabout 30 minutes or more, to obtain a substantially homogeneous, uniformmelt, followed by cooling the ink to ambient temperature (typically fromabout 20° C. to about 25° C.). The inks are solid at ambienttemperature. In a specific embodiment, during the formation process, theinks in their molten state are poured into molds and then allowed tocool and solidify to form ink sticks. Suitable ink preparationtechniques are disclosed in U.S. Pat. No. 7,186,762, the disclosure ofwhich is incorporated herein by reference in its entirety.

Such robust inks may be used with printing equipment at high speeds.Typically, production digital presses print at a speed comprised fromabout 100 to 500 or more feet/minute. This requires inks which arecapable of solidifying very fast once placed onto the paper, in order toprevent offset of the printed image during fast printing process, whereprinted paper is either stacked (cut-sheet printers) or rolled(continuous feed printers). Fast crystallization is not a general orinherent property of crystalline-amorphous robust inks. Therefore notall crystalline-amorphous inks are suitable for fast printing. Thepresent inventors have discovered specific crystalline sulfone compoundswhich when used in conjunction with specific amorphous compounds providefast crystallization, therefore enabling fast printing.

In order to evaluate the suitability of a test ink for fast printing aquantitative method for measuring the rates of crystallization of phasechange inks containing crystalline components was developed. TROM(Time-Resolved Optical Microscopy) enables comparison between varioustest samples and, as a result, is a useful tool for monitoring theprogress made with respect to the design of fast crystallizing inks.

TROM is described in co-pending U.S. patent application Ser. No.13/456,847 entitled “TROM Process for Measuring the Rate ofCrystallization of Phase change Inks” to Gabriel Iftime et al.,electronically filed on the same day herewith (Attorney Docket No.20110828-401275).

Time Resolved Optical Microscopy

TROM monitors the appearance and the growth of crystals by usingPolarized Optical Microscopy (POM). The sample is placed between crossedpolarizers of the microscope. Crystalline materials are visible becausethey are birefringent. Amorphous materials or liquids, similar to, forexample, inks in their molten state that do not transmit light, appearblack under POM. Thus, POM enables an image contrast when viewingcrystalline components and allows for pursuing crystallization kineticsof crystalline-amorphous inks when cooled from the molten state to aset-temperature. Polarized optical microscopy (POM) enables exceptionalimage contrast when viewing crystalline components.

In order to obtain data that allow comparison between different andvarious samples, standardized TROM experimental conditions were set,with the goal of including as many parameters relevant to the actualprinting process. The ink or ink base is sandwiched between 16-25 mmcircular thin glass slides of a thickness of 0.2 mm to 0.5 mm. Thethickness of the ink layer is kept at 5-25 μm (controlled withfiberglass spacers) which is close to actual printed ink layers. Forrate of crystallization measurement, the sample is heated to theexpected jetting temperature (viscosity of about 10-12 cps) via anoffline hotplate and then transferred to a cooling stage coupled with anoptical microscope. The cooling stage is thermostated at a presettemperature which is maintained by controlled supply of heat and liquidnitrogen. This experimental set-up models the expected drum/papertemperature onto which a drop of ink would be jetted in real printingprocess (40° C. for the experiments reported in this disclosure).Crystal formation and growth is recorded with a camera.

The key steps in the TROM process are illustrated in FIG. 2,highlighting the key steps in the measuring process with the mainlineink base which contains just amorphous and crystalline components (nodye or pigment). When viewed under POM, the molten and at time zero, thecrystalline-amorphous inks appear black as no light is passed through.As the sample crystallizes, the crystalline areas appear brighter. Thenumbers reported by TROM include: the time from the first crystal(crystallization onset) to the last (crystallization completion).

The definition of key measured parameters of the TROM process are setforth below:

-   Time zero (T=0 s)−the molten sample is placed on the cooling stage    under microscope-   T onset=the time when the first crystal appears-   T growth=the duration of the crystal growth from the first crystal    (T onset) to the completion of the crystallization (T total)-   T total=T onset+T growth

It should be understood that the crystallization times obtained with theTROM method for selected inks are not identical to what would be thecrystallization times of a droplet of ink in an actual printing device.In an actual printing device such as a printer, the ink solidifies muchfaster. We determined that there is a good correlation between the totalcrystallization time as measured by the TROM method and thesolidification time of an ink in a printer. In the standardizedconditions described above, we determined that inks solidify within10-15 second or less measured by the TROM method, are suitable for fastprinting, typically at speeds from 100 feet/minute or higher. Therefore,for the purpose of the present disclosure, a rate of crystallizationlower than 15 seconds is considered to be fast crystallizing.

In certain embodiments, the phase change ink crystallizes in less than15 seconds.

The inks can be employed in apparatus for direct printing ink jetprocesses and in indirect (offset) printing ink jet applications.Another embodiment disclosed herein is directed to a process whichcomprises incorporating an ink as disclosed herein into an ink jetprinting apparatus, melting the ink, and causing droplets of the meltedink to be ejected in an imagewise pattern onto a recording substrate. Adirect printing process is also disclosed in, for example, U.S. Pat. No.5,195,430, the disclosure of which is totally incorporated herein byreference. Yet another embodiment disclosed herein is directed to aprocess which comprises incorporating an ink as disclosed herein into anink jet printing apparatus, melting the ink, causing droplets of themelted ink to be ejected in an imagewise pattern onto an intermediatetransfer member, and transferring the ink in the imagewise pattern fromthe intermediate transfer member to a final recording substrate. In aspecific embodiment, the intermediate transfer member is heated to atemperature above that of the final recording sheet and below that ofthe melted ink in the printing apparatus. In another specificembodiment, both the intermediate transfer member and the finalrecording sheet are heated; in this embodiment, both the intermediatetransfer member and the final recording sheet are heated to atemperature below that of the melted ink in the printing apparatus; inthis embodiment, the relative temperatures of the intermediate transfermember and the final recording sheet can be (1) the intermediatetransfer member is heated to a temperature above that of the finalrecording substrate and below that of the melted ink in the printingapparatus; (2) the final recording substrate is heated to a temperatureabove that of the intermediate transfer member and below that of themelted ink in the printing apparatus; or (3) the intermediate transfermember and the final recording sheet are heated to approximately thesame temperature. An offset or indirect printing process is alsodisclosed in, for example, U.S. Pat. No. 5,389,958, the disclosure ofwhich is totally incorporated herein by reference. In one specificembodiment, the printing apparatus employs a piezoelectric printingprocess wherein droplets of the ink are caused to be ejected inimagewise pattern by oscillations of piezoelectric vibrating elements.Inks as disclosed herein can also be employed in other hot melt printingprocesses, such as hot melt acoustic ink jet printing, hot melt thermalink jet printing, hot melt continuous stream or deflection ink jetprinting, and the like. Phase change inks as disclosed herein can alsobe used in printing processes other than hot melt ink jet printingprocesses.

Any suitable substrate or recording sheet can be employed, includingcoated and plain paper. Coated paper includes silica coated papers suchas Sharp Company silica coated paper, JuJo paper, HAMMERMILL LASERPRINTpaper, and the like, glossy coated papers such as XEROX Digital ColorElite Gloss, Sappi Warren Papers LUSTROGLOSS, specialty papers such asXerox DURAPAPER, and the like. Plain paper includes such as XEROX 4200papers, XEROX Image Series papers, Courtland 4024 DP paper, rulednotebook paper, bond paper. Transparency materials, fabrics, textileproducts, plastics, polymeric films, inorganic recording mediums such asmetals and wood, may also be used.

The inks described herein are further illustrated in the followingexamples. All parts and percentages are by weight unless otherwiseindicated.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art, and are also intended to beencompassed by the following claims.

While the description above refers to particular embodiments, it will beunderstood that many modifications may be made without departing fromthe spirit thereof. The accompanying claims are intended to cover suchmodifications as would fall within the true scope and spirit ofembodiments herein.

The presently disclosed embodiments are, therefore, to be considered inall respects as illustrative and not restrictive, the scope ofembodiments being indicated by the appended claims rather than theforegoing description. All changes that come within the meaning of andrange of equivalency of the claims are intended to be embraced therein.

EXAMPLES

The examples set forth herein below and are illustrative of differentcompositions and conditions that can be used in practicing the presentembodiments. All proportions are by weight unless otherwise indicated.It will be apparent, however, that the present embodiments can bepracticed with many types of compositions and can have many differentuses in accordance with the disclosure above and as pointed outhereinafter.

Example 1

Preparation of Ink

Tri-DL-menthyl citrate (TMC) shown in U.S. patent application Ser. No.13/095,795 and di-DL-menthyl L-tartrate (DMT) shown in U.S. patentapplication Ser. No. 13/095,784 were employed as the amorphous componentof the ink formulation. Compound 1 and the amorphous materials werestirred in the molten state at 130° C. with no dye (for ink base) or 2wt % of Solvent Blue 101 dye (available from Keystone (Chicago, Ill.)),then cooled down to obtain the ink samples. The crystalline/amorphousratio of the ink samples were about 80/20 or about 70/30 in weightpercent. 2 grams of the ink base was formulated from 1.4 grams ofCompound 1 and 0.6 grams of TMC. 4 grams of each ink sample wereformulated from 3.14 grams of Compound 1, 0.78 grams of the amorphous,and 0.08 grams of Solvent Blue 101, or 2.74 grams of Compound 1, 1.18grams of the amorphous, and 0.08 grams of Solvent Blue 101. Thecrystalline and amorphous materials were well miscible in these mixingratios. The ink formulations are shown in Table 3.

TABLE 3 Ink Formulation (wt %) Diphenyl Solvent Sulfone Blue Ink ID(Compound 1) TMC* DMT* 101 T_(test) T_(onset) T_(growth) T_(total) Pure100 — — — 132 2 1 3 Crystalline Ink Base A 80 20   — — 130 2.5 2 4.5 InkSample A 78.4 19.6 — 2 130 3 2 5 Ink Sample B 78.4 — 19.6 2 120 4 2 6Ink Sample C 68.6 29.4 — 2 120 5 4 9 Ink Sample D 68.6 — 29.4 2 120 4 711 *Amorphous material.

Ink Properties (Rate of Crystallization and Rheology)

FIG. 3 shows DSC data of a representative ink sample comprising diphenylsulfone (Compound 1)/TMC/Solvent Blue 101 (68.6/29.4/2 (wt %)). BothT_(melt) and T_(crys) shifted to lower temperatures, but the samplestill showed remarkably sharp phase transitions even when mixed with theamorphous component and dye. The fast crystallization was confirmed byTime Resolved Optical Microscopy (TROM) measurements.

Table 3 shows the ink formulations and rate of crystallization data ofthe inks obtained by TROM. The rates of crystallization were notsignificantly influenced by the presence of the amorphous and dyecomponents.

As it can be seen from Table 3, all the crystalline-amorphousformulations containing sulfone crystalline component crystallized fast,at a Total time of crystallization of less than 15 seconds. They aretherefore suitable for printing at high speed rates of 100 feet perminute or more.

FIG. 4 shows rheology data of the ink samples. The inks showed phasetransition to greater than 1×10⁶ cps at a temperature between about 115°C. and 120° C. The phase transition temperature will be adjustable byselection of materials and changing the crystalline/amorphous ratiowithin the desirable temperature range (65° C.<T<130° C.). Furthermore,the viscosity above phase transition temperatures were below 10 cps andagain adjustable by changing the ratio or blending additives such as aviscosity modifier.

Print Performance

The ink was used for K-proof print test examination on coated paperXerox Digital Color Elite Gloss, 120 gsm (DCEG) by a K Printing Proofer(manufactured by RK Print Coat Instrument Ltd., Litlington, Royston,Heris, SG8 0OZ, U.K.) When a scratch/gouge finger with a curved tip atan angle of about 15° from vertical, with a weight of 528 g applied, wasdrawn across the image at a rate of approximately 13 mm/s. Thescratch/gouge tip is similar to a lathe round nose cutting bit withradius of curvature of approximately 12 mm.

Summary

In summary, the present embodiments provide robust phase change inkformulations developed for inkjet printing which contains at least onecrystalline material and at least one amorphous material. The inks mayalso include a colorant, such as a pigment or dye. The crystallinematerials are selected sulfone compounds or derivatives thereof whichhave demonstrated to have suitable properties for use as the crystallinecomponent in phase change ink compositions and are miscible with theamorphous materials. The resulting crystalline materials have desirablephysical properties which provide for robust and fast printing inks.

The claims, as originally presented and as they may be amended,encompass variations, alternatives, modifications, improvements,equivalents, and substantial equivalents of the embodiments andteachings disclosed herein, including those that are presentlyunforeseen or unappreciated, and that, for example, may arise fromapplicants/patentees and others. Unless specifically recited in a claim,steps or components of claims should not be implied or imported from thespecification or any other claims as to any particular order, number,position, size, shape, angle, color, or material.

All the patents and applications referred to herein are herebyspecifically, and totally incorporated herein by reference in theirentirety in the instant specification.

What is claimed is:
 1. A phase change ink comprising: an amorphouscomponent comprises an ester of tartaric acid of Formula II or an esterof citric acid of Formula III

 wherein R₁, R₂, R₃, R₄ and R₅ are independently an alkyl group, whereinthe alkyl can be straight, branched or cyclic, saturated or unsaturated,substituted or unsubstituted, having from about 1 to about 40 carbonatoms, or an substituted or unsubstituted aromatic or heteroaromaticgroup, and mixtures thereof; and a crystalline component being a sulfonecompound having the followingR₆—SO₂—R₇  Formula I wherein R₆ and R₇ can be the same or different, andwherein R₆ and R₇ each, independently of the other is selected from thegroup consisting of (i) an alkyl group, which can be a linear orbranched, cyclic or acyclic, substituted or unsubstituted, saturated orunsaturated, alkyl group, and wherein heteroatoms may optionally bepresent in the alkyl group having from about 1 to about 40 carbon atoms;(ii) an arylalkyl group, which can be a substituted or unsubstitutedarylalkyl group, wherein the alkyl portion of arylalkyl group can belinear or branched, cyclic or acyclic, substituted or unsubstituted,saturated or unsaturated, and wherein heteroatoms may optionally bepresent in either the aryl portion or the alkyl portion of the arylalkylgroup having from about 4 to about 40 carbon atoms; and (iii) anaromatic group, which can be a substituted or unsubstituted aromaticgroup, wherein the substituent can be a linear, branched, cyclic oracyclic alkyl group and wherein heteroatoms may optionally be present inthe aromatic group having from about 3 to about 40 carbon atoms, andmixtures thereof; wherein the phase change ink crystallizes in less than15 seconds.
 2. The phase change ink of claim 1, wherein the tartaricacid backbone is selected from L-(+)-tartaric acid, D-(−)-tartaric acid,DL-tartaric acid, or mesotartaric acid, and mixtures thereof.
 3. A phasechange ink comprising: an amorphous component comprises an ester oftartaric acid of Formula II or an ester of citric acid of Formula III

 wherein R₁, R₂, R₃, R₄ and R₅ are independently an alkyl group, whereinthe alkyl can be straight, branched or cyclic, saturated or unsaturated,substituted or unsubstituted, having from about 1 to about 40 carbonatoms, or an substituted or unsubstituted aromatic or heteroaromaticgroup, and mixtures thereof; and a crystalline component being a sulfonecompound having the following Formula IR₆—SO₂—R₇  Formula I each R₆ and R₇ is independently alkyl, or aryl,optionally substituted with one or more halo, amino, hydroxy, or cyanogroups and combinations thereof, or R₆ and R₇ taken together with the Satom to which they are attached form a heterocyclic ring; wherein thecrystalline and amorphous component are present in acrystalline/amorphous weight ratio of from about 60:40 to about 95:5. 4.The phase change ink of claim 3, wherein the crystalline component isselected from the group consisting of diphenyl sulfone, dimethylsulfone, bis(4-hydroxyphenyl) sulfone, bis(4-aminophenyl) sulfone,bis(3-aminophenyl) sulfone, bis(4-chlorophenyl) sulfone,bis(4-fluorophenyl) sulfone, 2-hydroxyphenyl-4-hydroxyphenyl sulfone,phenyl-4-chlorophenyl sulfone, phenyl-2-aminophenyl sulfone,bis(3-amino-4-hydroxyphenyl) sulfone, dibenzyl sulfone, methylethylsulfone, diethyl sulfone, methylisopropyl sulfone, ethylisopropylsulfone, di-n-butyl sulfone, divinyl sulfone, methyl-2-hydroxyethylsulfone, methylchloromethyl sulfone, sulfolane, 3-sulfolene, andmixtures thereof.
 5. The phase change ink of claim 3 being in solidstate at room temperature.
 6. The phase change ink of claim 3 having ajetting temperature of from about 100 to about 140° C.
 7. The phasechange ink of claim 3, wherein the amorphous and crystalline componentsare miscible in the liquid state.
 8. A phase change ink comprising: anamorphous component comprises an ester of tartaric acid of Formula II oran ester of citric acid of Formula III

 wherein R₁, R₂, R₃, R₄ and R₅ are independently an alkyl group, whereinthe alkyl can be straight, branched or cyclic, saturated or unsaturated,substituted or unsubstituted, having from about 1 to about 40 carbonatoms, or an substituted or unsubstituted aromatic or heteroaromaticgroup, and mixtures thereof; and a crystalline component being a sulfonecompounds having the following Formula IR₆—SO₂—R₇  Formula I wherein R₆ and R₇ can be the same or different, andwherein R₆ and R₇ each, independently of the other is selected from thegroup consisting of (i) an alkyl group, which can be a linear orbranched, cyclic or acyclic, substituted or unsubstituted, saturated orunsaturated, alkyl group, and wherein heteroatoms may optionally bepresent in the alkyl group having from about 1 to about 40 carbon atoms;(ii) an arylalkyl group, which can be a substituted or unsubstitutedarylalkyl group, wherein the alkyl portion of arylalkyl group can belinear or branched, cyclic or acyclic, substituted or unsubstituted,saturated or unsaturated, and wherein heteroatoms may optionally bepresent in either the aryl portion or the alkyl portion of the arylalkylgroup having from about 4 to about 40 carbon atoms; and (iii) anaromatic group, which can be a substituted or unsubstituted aromaticgroup, wherein the substituent can be a linear, branched, cyclic oracyclic alkyl group and wherein heteroatoms may optionally be present inthe aromatic group having from about 3 to about 40 carbon atoms andmixtures thereof.
 9. The phase change ink of claim 8, wherein each R₆and R₇ is independently phenyl or benzyl optionally substituted with oneor more halo, amino, hydroxy, cyano or combinations thereof.
 10. Thephase change ink of claim 8, wherein each R₆ and R₇ is independentlymethyl, ethyl, isopropyl, n-butyl, or vinyl optionally substituted withone or more hydroxyl, cyano, or combinations thereof.
 11. The phasechange ink of claim 8, wherein the crystalline component is present inan amount of from about 60 percent to about 95 percent by weight of thetotal weight of the phase change ink.
 12. The phase change ink of claim8, wherein the amorphous component is present in an amount of from about5 percent to about 40 percent by weight of the total weight of the phasechange ink.
 13. The phase change ink of claim 8 further comprising acolorant selected from the group consisting of a pigment, dye ormixtures thereof.
 14. The phase change ink of claim 8, wherein thecrystalline/amorphous ratio is from about 60:40 to about 95:5.
 15. Thephase change ink of claim 8, wherein the crystalline component has aviscosity of less than 10 cps at a temperature of about 140° C.
 16. Thephase change ink of claim 8, wherein the crystalline component hasT_(melt) of less than 150° C.
 17. The phase change ink of claim 8,wherein the crystalline component has T_(crys) of greater than 60° C.18. The phase change ink of claim 8 having a viscosity of from about 1to about 22 cps in a jetting range of from about 100 to about 140° C.19. The phase change ink of claim 8 having a viscosity of greater thanabout 1×10⁶ cps at room temperature.